A need exists within the automotive industry to increase the electrical power capability for future vehicles. For example, future vehicle concepts are being studied requiring increased voltage levels in direct current (DC) systems to as high as 42 volts, approximately three times greater than conventional 14 volt systems. The driving forces contributing toward this change are the need to reduce fuel consumption and the introduction of additional electrical features. New power networks must accommodate the increased energy demand of comfort and security devices as well as the electrical needs of major systems such as braking, electric power steering and suspension systems.
The introduction of a system voltage higher than approximately 20 volts causes considerable component and system changes and has the potential to significantly impact system reliability and safety. For example, one significant impact of the increase in system voltage to levels such as the envisioned forty-two volt, direct-current network is the need to address the increased potential for arcing (shorting over a finite gap) from and within the electrical distribution systems and components. One particularly vulnerable component of electrical systems are the wiring harnesses, wherein arc faults may be encountered as a result of cut, pinched or chaffed wiring. Accordingly, a substantial need exists to protect electrical distribution systems, and particularly wire harnesses, from unwanted arc faults.
In the instance of a wire being cut or broken under an electrical load, an arc may be drawn between both ends. Such an arc is unwanted and unplanned for, and its extinction is uncertain. Therefore, severe damage may occur if the arc is sustained. This type of arc fault is called a series arc fault, as the arc is in series to the load. Hot unplugs due to vibrating loose connections fall into the same series arc fault category. Series arc faults cannot typically be cleared by fuses or circuit breakers.
Arc faults in parallel to the load are identified as parallel arc faults. An example of parallel arc faults can be damaged wires drawing an arc to a ground potential, such as a chassis of an automobile. The insulation jacket of such wires might be broken due to aging or shaved, chaffed or pinched cable jackets. This type of arc fault is usually created by a temporary short circuit. The arc fault current, however, may thermally over load and damage contacts within the circuit due to low contact force resulting in melting and evaporating contact material followed by more arcing. The arc fault current, limited by the circuit impedance and the arc voltage, can be significantly lower than the trip current of the protection device such as a fuse or circuit breaker, so that the fault is cleared late depending on the time or current characteristics or in some cases not at all.
Many patents disclose arc fault detection systems and methods for alternating current (AC) applications. However, fewer arc detection devices and methods are disclosed for direct current (DC) applications.
Consequently, there remains a need in the art for arc detection and protection systems and methods for DC circuits capable of rapidly detecting both parallel and series arcs. It would be beneficial to have a system and method capable of distinguishing unwanted and unplanned arcs from expected transient arcs such as those caused by the opening of a load switch. It would be further beneficial to utilize arc detection components such as sensors that are small so that they can be incorporated in devices such as electrical connectors, junction blocks, relays, circuit breakers, and the like. It would also be desirable to have a systems and methods continuously monitoring for arcing conditions rather than periodically sampling. It would further be desirable to have an arc detection and protection system that uses low cost components without requiring the use of microprocessors or complex algorithms.